It couldn’t be better 为什么用过去式

It couldn’t be better 为什么用过去式 It couldn't be any worse It couldn't be any better 如果把any去掉, It couldn't be better,you're the best.翻译 it couldn,t be better,but iknow,it wouldn,t be any I couldn’t have said it better. it couldn't be any worse any为什么不是so it couldn't be used then The box was so heavy that I couldn't lift it .中为什么用couldn't i couldn't have put it better 请高手回答, I couldn't have put it better myself couldn't 同义句为什么要变过去式 life couldn't get better